Screening Early-Generation Progenies of Interspecific Rice Genotypes for Drought-Stress Tolerance During Vegetative Phase

Abstract

Drought is an important production constraint in rice (Oryza sativa L.) in Africa. A breeding approach is needed to improve traditional rice by introgression of new genes for drought tolerance and high yield at early generation to enhance production. This study was conducted to identify drought-tolerant progenies in early generations and to establish a relationship between drought tolerance and some morphological and physiological traits. Interspecific progenies were generated using North Carolina II mating design and were advanced to F₃ and F₄ generations. Progenies were evaluated in 8 × 8 and 9 × 9 simple-lattice designs under managed drought stress and fully irrigated conditions, respectively. Overhead sprinkler irrigation was applied till maximum tillering stage (35 d after sowing) and stopped in the stress experiment for 50 d to induce stress and resumed thereafter until maturity. Significant differences were detected among genotypes for drought tolerance, and tillering and flowering dates. Selection indices ranging from –42.74 to 20.70 were therefore used to rank the progenies. Drought stress delayed flowering and was more pronounced in early- than late-flowering progenies. High-tillering progenies had larger reduction in tiller number than low-tillering progenies under stress. Drought tolerance (little leaf drying), taller plants and less leaf rolling were significantly associated with rapid ability to recover at 3 d and 10 d after drought-stress relief. The putative traits identified could be used as indicators of drought stress tolerance in a breeding program.

KEYWORDS:

• Drought tolerance
• interspecific rice
• putative traits
• ability to recover

The authors thank The Rockefeller Foundation, New York, for supporting this research.